I'm just curious as to what people are seeing in fuel efficiency improvements (if any) after installing a Y-pipe and intake. Theoretically, you should be seeing some improvements.

Of course we know there will be power gains which in turn may make people drive a bit more aggressively for fun which may counteract fuel efficiency gains.

 

I don't have a Y-Pipe but I do have a high flow air filter adapted to my MAF sensor and I don't see any improved mileage, even when I drive like a normal person.

 

i have had my y-pipe on for about a week now and it hasnt increased my miles per tank at all.

 

I've have had a Y-pipe on for about a year and it doesn't make a difference in fuel economy one way or the other.

 

i think it depends on the driver....i would get great gas mileage if i drove like a grandma....but who likes to drive slow...btw i have ypipe exhaust and intake.

but i did see a significant increase in about 30+ miles with the addition of the catback exhaust....ypipe and intake no gains....

 

it all depends on the driver and the way they drive their car. also local/hwy driving as well.

 

I realize that driving habits will affect mileage but assuming the person drives the same way with the same split between city and hwy miles, would there be any gains with an intake and a Y-pipe?

Doesn't sound like there is.

 

is their any math?
a y-pipe will net you on average ~12 to 15hp or so
an intake about 6hp max at the high end.

what is the math to figure this out (in theory, obviously it wouldnt be 100% true).

 

don't mean to steal the thread, i got a quick question. I'm in the process of installing my y-pipe and the bolts connecting to the catalytic conv. are no good.
Are there special bolts i should use for exhaust components b/c of the extreme heat or are the home depot bolts fine?

 

home depot bolts are fine... or ask a muffler shop

 

for people who have a Y-pipe...do you realy notice a big difference when you put it on? i know its the best or one of the best performance mods but how much do you feel it? just wondering not realy important though

 

ill be able to answer that tmrw for ya after i install my y-pipe

 

yeah there is a difference...throttle response...sound...thats about it...

 

maybe you're thinking of hacked air box...

 

Everyone I've spoken to has said that the Y-pipe has definitely given them a performance increase. I'm sure there are Dyno charts to prove this beyond a reasonable doubt.

Based on what I've read, I think there is more to it than just throttle response and sound.

 

What kind of math were you looking for? I don't see how horsepower gains directly translate into fuel efficiency. For instance, you could have a 160 horsepower engine get your more miles to the gallon than an engine with 140 hp. Depends on a lot of different factors.

I was posing a question about fuel efficiencies with the same car with the same commute and same driving habits with and without an intake and a y-pipe.

 

yes, some math could be derived. When the Nissan engineers design the car, they come up with a system of equations for everything, including fuel consumption and efficiency.

Some of the factors include air temperature, tire pressure, intake flow, type of gas (did you know that typical summer gasoline contains a little bit more energy than winter gasoline?), friction between various internal components, etc. There are probably 100+ variables. So while it would be possible for us (without having Nissan's test data) to derive an equation to model fuel efficiency, it's just too complicated to do.
And if you're wondering, yes, I'm an engineer.

 

thanks buddy.. i know theirs way to many factors, but something in theory would help.

honestly i dont care, just wana help the guy... looks like he doesnt care tho

 

so am i

 

Don't get me wrong, I appreciate everyone's input. I'm an engineer also and even I wouldn't want to touch the calculations required to get a theoretical handle on fuel efficiency differences with and without a Y-pipe and intake. Without the right data and assumptions, any calculation results I could come up with would probably contain such a high % error that it would be almost a useless exercise anyways. As was mentioned earlier, there are a lot of parameters that go into such calculations.

The best way to do it is just to see if anyone has kept record of fuel efficiencies before and after these mods. Doesn't look like anyone is reporting anything substantial though.

Thanks to all for your input.